1. Field of the Invention
The invention relates to an improved process for the preparation of alkali-metal formyl acetic acid esters from acetic acid esters, alkali-metal alcoholate and carbon monoxide which employs elevated temperature and elevated pressure.
2. Discussion of Prior Art
From U.S. Pat. No. 2,394,255 it is known to react acetic acid esters with alkali-metal alcoholate e.g. sodium alcoholate in the presence of alkyl formate or carbon monoxide, or preferably alkyl formate and carbon monoxide. There an excess of sodium alcoholate with respect to acetic acid ester is used, and alkyl formate or methanol, which in the presence of carbon monoxide forms alkyl formate, are also present.
The reaction product is a slurry, in other words a suspension of solids in excess alkyl formate and alkali-metal alcoholate, which is difficult to work up to give sodium formyl acetic ester. According to U.S. Pat. No. 2,394,255, the slurry is therefore reacted to give a secondary product. Yield and purity thus are unsatisfactory, and the alkyl formate and sodium alcoholate losses are substantial.
In accordance with German No. 708,513, sodium ethylate and ethyl acetate in a mol ratio of 1:1 are reacted with carbon monoxide in the presence of large amounts of alcohol as solvent. A yield of 85% of a substance of unspecified purity which is convertible to oxymethylene acetic acid ethyl ester only to the extent of 17% is obtained.